A highly active Fe(I) catalyst for radical polymerisation and taming the polymerisation with iodine

A fast and controlled radical polymerisation of acrylates and acrylamides can be achieved with a combination of a highly active metal catalyst, Fe2Cp2(CO)4, and a mild radical scavenger, iodine, in the presence of an iodide initiator.     

Determination of micro-amounts of sulphur in organic compounds by combustion and reduction

Summary A rapid sensitive method for the determination of microgram amounts of sulphur is described. Sulphur (free or combined) in organic substances is oxidised completely in an oxygen atmosphere over a platinum gauze catalyst after a preliminary incomplete combustion in air. The oxides of sulphur are collected on silver gauze at 550°. The oxygen is purged from the apparatus with a stream of nitrogen and then the silver sulphate is heated in a stream of hydrogen to yield hydrogen sulphide which is collected in an alkaline zinc acetate solution and subsequently determined spectrophotometrically by the methylene blue method.The recovery of sulphur in the range 5–40g was 100±5%. The method takes less than 25 minutes for a single determination and is reliable for the determination of as little as1 g of sulphur in all types of organic compounds. Solid, liquid, or gaseous samples may be used.

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Zusammenfassung Eine schnelle, empfindliche Methode zur Bestimmung von Mikrogrammmengen Schwefel wurde beschrieben. Freier oder gebundener Schwefel in organischem Material wird nach unvollständiger Verbrennung in Luft in Sauerstoffatmosphäre über einem Platindrahtnetz vollständig oxydiert. Die Schwefeloxide werden auf Silberdrahtnetz bei 550° gebunden. Der Sauerstoff wird mit Stickstoff aus der Apparatur gespült und dann das Silbersulfat im Wasserstoffstrom zu Schwefelwasserstoff reduziert, der in alkalischem Zinkacetat aufgefangen und dann nach der Methylenblaumethode spektrophotometrisch bestimmt wird.In der Größenordnung zwischen 5 und 10g wird der Schwefel zu 100±5% erfaßt. Eine Einzelbestimmung dauert weniger als 25 Minuten. Für alle Arten organischer Verbindungen, ob fest, flüssig oder gasförmig, eignet sich das Verfahren für die Bestimmung von 1g Schwefel und darüber.

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Résumé On décrit une méthode rapide et sensible pour le dosage de quantités de soufre de l'ordre du microgramme. Le soufre (libre ou combiné) dans les substances organiques est oxydé complètement en atmosphère d'oxygène sur une toile de platine, catalyseur, après une combustion préliminaire incomplète dans l'air. Les oxydes du soufre sont rassemblés sur une toile d'argent à 550°. On purge l'appareil de l'oxygène par un courant d'azote puis le sulfate d'argent est chauffé dans un courant d'hydrogène en donnant de l'hydrogène sulfuré qui est rassemblé dans une solution alcaline d'acétate de zinc et dosé ensuite par spectrophotométrie par la méthode au bleu de méthylène.La récupération du soufre entre 5 et 40g atteint 100±5%. La méthode demande moins de 25 minutes pour un dosage individuel et reste valable pour les teneurs descendant jusqu'à 1g de soufre dans les composés organiques de toutes natures. On peut utiliser des échantillons solides, liquides ou gazeux.

     

Catalytic activity of binuclear planar copper(II) complexes for the decomposition of hydrogen peroxide

Planar binuclear copper(II) complexes generally showed high catalytic activities for the decomposition of hydrogen peroxide compared with the relevant planar mononuclear copper(II) complexes. This result was explained on the assumption that the two-electron transfer occurs between H₂O₂ molecules via an intervening binuclear copper(II) complex.     

Luminescence of high density electron-hole plasma in CdSe at elevated temperature

Luminescence of high density electron-hole plasma in CdSe is observed in the 77–300 K temperature range by picosecond pulse excitation. With increasing temperature from 77 K the stimulated emission band is replaced by the spontaneous emission band. Temperature changes of spectral features of these two bands and also their time dependence after pulse excitation are consistent with the theoretical consideration.     

Synthesis, inhibitory effects on nitric oxide and structure-activity relationships of a glycosphingolipid from the marine sponge Aplysinella rhax and its analogues

The novel glycosphingolipid, β-D-GalNAcp(1-->4)[α-D-Fucp(1-->3)]-β-D-GlcNAcp(1-->)Cer (A), isolated from the marine sponge Aplysinella rhax has a unique structure, with D-fucose and N-acetyl-D-galactosamine moieties attached to a reducing-end N-acetyl-D-glucosamine through an α1-->3 and β1-->4 linkage, respectively. We synthesized glycolipid 1 and some non-natural di- and trisaccharide analogues 2-6 containing a D-fucose residue. Among these compounds, the natural type showed the most potent nitric oxide (NO) production inhibitory activity against LPS-induced J774.1 cells. Our results indicate that both the presence of a D-Fucα1-3GlcNAc-linkage and the ceramide aglycon portion are crucial for optimal NO inhibition.     

High-yield synthesis of semiconductive type-II Si clathrates with low Na content

To develop an efficient synthesis of type-II Si clathrates with low Na content (Na_xSi₁₃₆: x = 0–24), various conditions for annealing the Zintl phase NaSi were examined. The addition of a pre-annealing process under vacuum at 250 °C following the preparation of NaSi resulted in a decrease in the Na content of type-II Si clathrates from 4 to 2 when the pre-annealing duration ranged from 0 to 60 h, while the volume fraction of type-II Si clathrate crystals in the synthesized specimens (type-II/(type-I + type-II + d-Si)) deduced by powder X-ray diffraction and Rietveld analysis was maintained at approximately 85%. These preparation techniques that enable the high-yield synthesis of semiconductive type-II Si clathrates open opportunities for the application of these substances to semiconductor devices.     

Necessary conditions for dominating the James-Stein estimator

This paper develops necessary conditions for an estimator to dominate the James-Stein estimator and hence the James-Stein positive-part estimator. The ultimate goal is to find classes of such dominating estimators which are admissible. While there are a number of results giving classes of estimators dominating the James-Stein estimator, the only admissible estimator known to dominate the James-Stein estimator is the generalized Bayes estimator relative to the fundamental harmonic function in three and higher dimension. The prior was suggested by Stein and the domination result is due to Kubokawa. Shao and Strawderman gave a class of estimators dominating the James-Stein positive-part estimator but were unable to demonstrate admissiblity of any in their class. Maruyama, following a suggestion of Stein, has studied generalized Bayes estimators which are members of a point mass at zero and a prior similar to the harmonic prior. He finds a subclass which is minimax and admissible but is unable to show that any in his class with positive point mass at zero dominate the James-Stein estimator. The results in this paper show that a subclass of Maruyama's procedures including the class that Stein conjectured might contain members dominating the James-Stein estimator cannot dominate the James-Stein estimator. We also show that under reasonable conditions, the “constant” in shrinkage factor must approachp-2 for domination to hold.     

An admissibility proof using an adaptive sequence of smoother proper priors approaching the target improper prior

A sufficient condition for the admissibility of generalized Bayes estimators of the location vector of spherically symmetric distribution under squared error loss is derived. This is as strong a condition as that of Brown [L.D. Brown, Admissible estimators, recurrent diffusions, and insoluble boundary value problems, Ann. Math. Statist. 42 (1971) 855–903] under normality. In particular we establish the admissibility of generalized Bayes estimators with respect to the harmonic prior and priors with slightly heavier tails than the harmonic prior. The key to our proof is an adaptive sequence of smooth proper priors approaching an improper prior fast enough to establish admissibility.     

An Integrated Circuit for Two-Dimensional Edge-Detection with Local Adaptation Based on Retinal Networks

We designed an integrated circuit for edge detection of a two-dimensional image based on the vertebrate outer retina, which has wide dynamic range in image processing. The unit circuit is simple, and operates as a current-mode analog metal-oxide-semiconductor (MOS) circuit. In order to extract edges from an image composed of bright and dark domains, the circuit realizes a function called local adaptation in which the sensitivity adapts to local brightness of the image. Simulation results, using the simulation program with integrated circuit emphasis (SPICE), of two-dimensional Gaussian-distributed images in which the intensity ranged over four orders of magnitude, showed the local adaptation. As a result, the intensity of output images was in the range of one order of magnitude. Furthermore, as the simulation result of real images, it was shown that edges in the dark domain, which was five times darker than the bright domain, were successfully detected as the bright domain in which input photocurrents ranged over two orders of magnitude.     

Analog Integrated Circuit for Motion Detection with Simple-Shape Recognition Based on Frog Vision System

We proposed in this research a novel two-dimensional network based on the frog visual system, with a motion detection function and a newly developed simple-shape recognition function, for use in object discrimination by integrated circuits. Specifically, the network mimics the signal processing of the small-field cell in a frog brain, consisting of the tectum and thalamus, which generates signals of the motion and simple shape of an object. The proposed network is constructed from simple analog complementary metal oxide semiconductor (CMOS) circuits; a test chip of the proposed network was fabricated with a 1.2 μm CMOS process. Measurements on the chip clarified that the proposed network can generate signals of the moving direction, velocity, and simple shape, as well as perform information processing of the small-field cell. Results with the simulation program with integrated circuit emphasis (SPICE) showed that the analog circuits used in the network have low power consumption. Applications of the proposed network are expected to realize advanced vision chips with functions such as object discrimination and target tracking.